7. Combining photocatalysis with other processes

To overcome some of the disadvantages of photocatalysis for air treatment, it is possible to combine this treatment with other processes.

Many systems offer mechanical filtration prior to photocatalysis. These are generally high-efficiency filters (classes F5-F9) for particles from 1 to 10 μm, with or without pre-filters. For certain indoor air applications, such as in the medical field, very high efficiency "HEPA" filters (class H10-H13) may be considered for their specific advantages. Electrostatic or ion-generator filtration processes are also used, with the risk of the formation of a secondary pollutant, ozone, partially degraded by photocatalysis and which can contribute to the degradation of pollutants on the catalyst.

The most frequent combination is coupling with adsorption. The most commonly used materials are activated carbons,...